Bar screen



June 11, 1963 E -r 3,093,580

BAR SCREEN 2 Sheets-Sheet 1 Filed June 9, 1960 INVENTOR.

N. R. SIEWERT June 11, 1963 N. R. SlEWERT BAR SCREEN 2 Sheets-Sheet 2 Filed June 9, 1960 INVENTOR.

N. R. SIEWERT A tfim'ncj FIG. 3

United States Patent 3,093,580 BAR SCREEN Norman R. Siewert, Rochester, N.Y., assignor to Klneflow Corporation, Rochester, N.Y., a corporation of New York Filed June 9, 1960, Ser. No. 34,991 8 Claims. (Cl. 210-159) The present invention relates to bar screens of the type employed for removing undesirable material from flowing liquids, and more particularly from sewage prior to treatment, to prevent objectionable material from reaching the sewage pumping and treatment machinery.

The conventional bar screen comprises a member that has a plurality of closely spaced parallel bars that are mounted in the path of the sewage flow, usually in the inverter of a manhole. The closely spaced bars of the screen are designed to remove from the sewage large objects which would be likely to impair the operation of the pumps or other sewage machinery. These screens get clogged in the course of time with large objects, paper, and the like. Periodically, it is necessary, therefore, to clean the screens manually, to remove from them matter which is too large to pass through the bars, and also to clean the bars of sticky material, such as animal waste, fish skins and the like which adhere to and build up on the bars.

In some instances, to avoid the cost, labor, and annoyance of hand-cleaning the bars, expensive complicated comminutors have been installed in sewage lines to shred and break up objectionable material into pieces small enough to be safely handled by the sewage machinery. Self-cleaning bar screens have been developed, also, but those known have not proved satisfactory enough heretofore to replace the usual hand-cleaned screen. They are heavy and expensive, complicated, and of a size to project far above the level of the liquid in the sewer, so as to be unsightly and oifensive from a public standpoint. Moreover, these prior self-cleaning screens were ineffective to clean off the sticky waste material that clung to and built up on the surfaces of the bars.

The primary object of the present invention is to provide an improved self-cleaning type bar screen.

To this end, another object of this invention is to provide an improved bar screen which will prevent waste material that is sticky or pasty from building up on the bars.

Still another object of this invention is to provide an improved self-cleaning bar screen provided with means for chopping up foreign bodies or large pieces of material that are caught on the screen and that otherwise would not flow through the spaces between the bars of the screen.

A further object of this invention is to provide a selfcleaning bar screen which is compact, has relatively few moving parts, which is simple in construction and relatively inexpensive to manufacture.

Other objects of this invention will become apparent from the specification, the accompanying drawings, and the appended claims.

In the drawings:

FIG. 1 is a side elevation of a bar screen constructed according to one embodiment of this invention, showing it installed in a sewer manhole;

FIG. 2. is a fragmentary front elevation of the bar screen showing the sliding grid of the screen between the upper and lower limits of its travel; and

FIG. 3 is a fragmentary sectional view taken online at-3 of FIG. 1 and looking in the direction of the arrows.

In the embodiment of the invention illustrated, a sta- Patented June 11, 1963 tionary grid, comprising a plurality of spaced parallel bars, is rigidly fastened across a conduit or inverter leading to the sewage treatment or purification machinery in a position inclined to the horizontal. Another grid having an equal number of spaced bars is mounted to slide on the bars of the stationary grid. The movable grid is alternately lifted and dropped. It has an arm that is positioned to be engaged by the roller of a crank arm as the crank arm rotates. As the crank arm revolves, the roller engages under the arm of the movable grid, and lifts this grid up until the roller rides free of the grid arm. The movable grid then drops down with a thud, sliding on the bars of the stationary grid. As the crank arm continues to revolve the slidable grid is picked up again, again lifted, and again released and dropped. The lower ends of the bars of the movable grid are sharpened to cut up, as the movable grid drops, any large pieces of material that are caught on the bars of the stationary grid. A resilient nylon pad is mounted in the bottom of the inverter or conduit in position to be struck by the lower ends of the bars of the movable grid at the end of its downward movement. The force with which the movable grid hits the pad sets up a vibration in the bars of the movable grid. These vibrations shake off excrement and the like. The roller on the crank arm, which lifts the movable screen upwardly, is olfset laterally from the vertical center line of the movable screen so that the tines or bars of the movable grid wipe across the bars of the stationary grid during ascent of the movable grid, thereby providing a shearing action to cut loose any material caught on either grid. Notches are provided on the back faces of the bars of the movable grid to further aid this shearing action. The described lateral shift of the movable grid also has the effect of moving large pieces of material caught by the points of its tines or bars laterally so that on the next drop of the movable screen the points of the tines strike these pieces in different places than from where they struck in the preceding drop. This expedites break up of this material and its flow-off with the liquid.

Referring now to the drawings by numerals of referonce, 10 denotes a sewer inlet conduit which leads to a manhole 11 which has side walls 16 and a sloping concrete bottom 12. A conduit 14 is the outlet through which the sewage flows to a pumping station or to treatment apparatus. Spaced above the conduits 10 and 14, and supported by the side walls 16 of the manhole is a horizontally disposed grating 18 from which the bar screen of the present invention is suspended.

This bar screen, designated as a whole at 20, is mounted in the manhole 11 between the inlet and outlet conduits 10 and 14 in the path of the sewage flow. It comprises a fixed grid 22 and a slidable grid 24. The grid 22 comprises a plurality of spaced parallel bars 25 which are of rectangular shape in cross-section and which are fastened at their tops to a flat crossbar 26, at their bottoms to a flat bar or strap 28, and intermediate their tops and bottoms to a flat bar 29 which has parallel, rearwardly-projecting, integral lugs 34 formed on it at its opposite ends. The bars 25 are spaced apart a distance to screen out and stop flow therebetween of any pieces of material which are of a size greater than can be handled by the pumps or treatment apparatus. The grid 22 is rigidly mounted across the path of sewage fiow by bolting or otherwise fastening the top crossbar 26 to an angle-iron bracket 32 that is fastened to the platform or grating 1'8, by bolting or otherwise fastening lugs 34 to opposite side walls of the manhole, and by securing the bar 28 at the lower end of the grid in an angle-iron seat 38 which is firmly embedded in the concrete bottom 12 of the manhole.

The movable grid 24 comprises a plurality of parallel bars 40 which are of rectangular shape in cross-section and which are spaced apart the same distance as the bars 25. The bars 40 are fastened together at their tops by a flat strap or crossbar 42 and intermediate their ends at some considerable distance from their bottoms by a flat strap or crossbar 44. They are sharpened at their lower ends 46. This grid 24 is positioned relative to grid 22 so that the rear surfaces 48 of the bars 40 abut against and ride on the front surfaces 56 of the bars 25. The bars 40 have a plurality of spaced semi-circular notches 52 in their rear faces to provide a plurality of cutting edges for wiping off the bars 25 any film or material deposited thereon.

Separation of the grid 24 from the grid 22 during sliding of grid 24 on grid 22 is prevented by a plurality of brackets 54 which are attached to the opposite ends of the straps or crossbars 40 and 42. These stop brackets have flange portions 56 which extend behind the opposite side bars 25 of the grid 22. The brackets 54 are spaced from the opposing surfaces of the side bars 25 of grid 22 to permit slight lateral shifting of the bars 40 relative to the bars 25 during operation of the screen.

The movable grid 24 is driven from a motor-gear reduction unit 62, which is mounted on the grating 18. A crank arm 66 is secured to the driven shaft 64 of this unit. This crank arm, which is driven by the gear reduction unit 62 at a relatively slow speed, such as 1% revolutions per minute, has a roller or cam follower 68 fastened adjacent its free end. This roller is adapted to cooperate with an angle-iron strap or arm 72 which is mounted at one side of the grid 24 to project forwardly therefrom. Angle-iron strap 72 is secured to an angleiron strap 70 which is mounted to one side of the longitudinal center of the grid 24 and which is rigidly attached to strap members 42 and 44 of this grid. The cooperating parts are so disposed that during a portion of each revolution of arm 66, its roller or pin 63 engages under and lifts the grid 24 upwardly relative to grid 22. When the roller or pin or cam follower 68 rides clear of the arm 72, however, the grid 24 is released and drops down by its own weight with a thud from the position shown in FIG. 2 to that shown in FIG. 1.

Secured the angle-iron bracket 38 is an elongate nylon block 80. This is positioned to be struck by pointed ends 46 of the bars 40 at the bottom of the travel of the grid 24.

The liquid sewage, which contains large particles of waste material including sticky and pasty substances, continually flows from conduit over the sloping surface 12. The liquid, and the particles, which can pass between the bars 25 and 4t), flow into the conduit 14. The large pieces are, however, caught on and blocked by the bars 25.

In operation of the screen, the reduction unit 62 is driven to rotate the arm 66 in a counterclockwise direction as viewed in FIG. 1 so that periodically the pin or cam follower 68 engages under the'arm 72 to lift the grid 24 upwardly. The offset position of the arm 70 causes the bars 40 to shift laterally slightly relative to bars 25 during the lifting of the grid 24. This lateral shifting not only pushes the large pieces of waste material laying on the nylon block laterally, but also creates a shearing motion to cut up the material lodged between the bars.

When the arm 66 has rotated far enough on each revolution for the pin or cam follower 68 to disengage the arm 72, the grid 24 drops. As it drops, the bars 40 shift laterally relative to the bars 25 to provide a shearing motion in the opposite direction to scrape or chop material caught thereon off the bars 25. The notches 52 in bars 40 assist in this scraping or chopping action. As the grid 24 drops also, material adhering to the bars 25 will be caught and dragged along by the pointed ends 46 of bars 40. At the end of the downward movement of grid 24 these pointed ends 46 will strike and cut up this material and any material lying over the pad 80. Moreover, when the ends 46 strike the nylon pad 80, vibrations will be set up in the bars 40 which for the portions thereof that extend below bar 44 are like tines of a fork, and matter adhering to the bars will be shaken loose. These vibrations, which are of relatively high frequency, will cause the adhering material to shake itself loose. Any material, which still adheres to the movable grid 24 on its next upward stroke, will be dislodged by the lateral motion of the grid and drop back onto the nylon pad and the bottom 12 of the manhole, so that it will be in a different position when the grid 24 drops again. Hence the points 46 of the bars 40 will strike this material in a different place from where they struck on the previous down stroke of the grid so as to further assist in breaking up the material.

Thus, I have provided an improved bar screen which effectively chops up the large particles yet does not require sharpening, which is self-cleaning even of the sticky material, and which is simple in its construction, and foolproof in its operation.

While the invention has been described in connection with a self-cleaning bar screen for use in sewage conduits, it will be understood that screens of the type described may be used in fiumes and elsewhere where it is desired to screen undesirable material from flowing liquid and that material may adhere to the screen.

While the invention has been described in connection with a specific embodiment thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

l. A bar screen for sewage conduits comprising a fixed grid and a movable grid, said fixed grid comprising a plurality of laterally spaced, parallel, upwardly-extendingibars mounted in the path of sewage flow and inclined to the direction of said flow, said movable grid comprising a plurality of laterally spaced, parallel upwardly-extending bars connected together to move as a unit and spaced from one another in correspondence to the spacing of the bars of said fixed grid, said movable grid being disposed at the upstream side of said fixed grid and the bars of said movable grid being in contact with the corresponding bars of said fixed grid so that the bars of said movable grid overlie and ride on the bars of said fixed grid upon movement of said movable grid, means for alternately lifting said movable grid upwardly and letting it drop back again by gravity to its starting position, said means imparting a slight lateral wiping motion to said movable grid to cause the bars theerof to wipe across the bars of said stationary grid at least on the upward movement of said movable grid thereby to produce a shearing action between the bars of the two grids, the lower ends of the bars of said movable grid being free to vibrate, and means positioned to be engaged by said movable grid at the end of the downward drop of said movable grid to impart vibration to said lower ends of the bars of said movable grid.

2. A device as claimed in claim 1 wherein the vibration producing means includes a resilient nylon block fixedly mounted at the bottom of the path of movement of said movable grid to be struck by the lower ends of said bars of said movable grid at the end of each do-wnstroke.

3. A bar screen as claimed in claim 2 wherein the bars of said movable grid are secured together at points remote from their lower ends so as to leave the lower portions of these bars free to vibrate, and wherein the lower ends of these bars are pointed to cut into material lying beneath them as said movable grid falls.

4. A her screen for removing undesirable solids from a flowing liquid stream comprising a fixed grid and a movable grid each of which is adapted to be positioned transverse to the path of flow of said stream, said fixed grid comprising a plurality of laterally spaced, parallel bars that are rigidly secured together, said movable grid comprising a plurality of parallel bars that are secured together to move as a unit and that are laterally spaced from one another in correspondence with the lateral spacing of the bars of said fixed grid, said movable grid being disposed at the upstream side of said fixed grid and with its bars in contact with the corresponding bars of said fixed grid so that the bars of said movable grid overlie, engage, and ride on the bars of said fixed grid on movement of said movable grid, the bars of said movable grid being secured together at points above and remote from their lower ends so that the lower portions of these bars are free to vibrate, and means for alternately lifting said movable grid upwardly on said fixed grid and letting said movable grid drop back again by gravity to its starting position, said means imparting a slight lateral wiping movement also to said movable grid relative to said fixed grid at least on the upward movement of said movable grid to cause the bars of said movable grid to Wipe across the associated bars of said fixed grid, thereby to produce a shearing action between the bars of the two grids, and a block mounted at the bottom of 6 said fixed grid in position to be struck by the bottom ends of the bars of said movable grid, when said movable grid is dropped, to set up vibrations in the lower portions of the bars of said movable grid, thereby to loosen matter which tends to cling to these bars.

5. A bar screen as claimed in claim 4 wherein said means comprises a rotary crank arm, an arm projecting at right angles from said movable grid at a point offset from the vertical center line of said movable grid, a pin carried by said crank arm and disposed at right angles to said crank arm to periodically engage and disengage the second-named arm as said crank arm rotates, and means for rotating said crank arm about an axis parallel to said pin.

6. A bar screen as claimed in claim 4 wherein the bars of one grid have notches in the surfaces thereof that are in contact with the bars of the other grid, said notches providing cutting edges.

7. A bar screen as claimed in claim 6 wherein said notches are provided in the rear faces of the bars of the movable grid.

8. A bar screen as claimed in claim 7 wherein the lower ends of the bars of said movable grid are pointed to chop up, at the end of the downward travel of said movable grid, solids deposited against said fixed grid.

References Cited in the file of this patent UNITED STATES PATENTS 1,698,387 Broome Jan. 8, 1929 

1. A BAR SCREEN FOR SEWAGE CONDUITS COMPRISING A FIXED GRID AND A MOVABLE GRID, SAID FIXED GRID COMPRISING A PLURALITY OF LATERALLY SPACED, PARALLEL, UPWARDLY-EXTENDING BARS MOUNTED IN THE PATH OF SEWAGE FLOW AND INCLINED TO THE DIRECTIO OF SAID FLOW, SAID MOVABLE GRID COMPRISING A PLURALITY OF LATERALLY SPACED, PARALLEL UPWARDLY-EXTENDING BARS CONNECTED TOGETHER TO MOVE AS A UNIT AND SPACED FROM ONE ANOTHER IN CORRESPONDENCE TO THE SPACING OF THE BARS OF SAID FIXED GRID, SAID MOVABLE GRID BEING DISPOSED AT THE UPSTREAM SIDE OF SAID FIXED GRID AND THE BARS OF SAID MOVABLE GRID BEING IN CONTACT WITH THE CORRESPONDING BARS OF SAID FIXED GRID SO THAT THE BARS OF SAID MOVABLE GRID OVERLINE AND RIDE ON THE BARS OF SAID FIXED GRID UPON MOVEMENT OF SAID MOVABLE GRID, MEANS FOR ALTERNATELY LIFTING SAID MOVABLE GRID UPWARDLY AND LETTING IT DROP BACK AGAIN BY GRAVITY TO ITS STARTING POSITION, SAID MEANS IMPARTING A SLIGHT LATERAL WIPING MOTION TO SAID MOVABLE GRID TO CAUSE THE BARS THEREOF TO WIPE ACROSS THE BARS OF SAID STATIONARY GRID AT LEAST ON THE UPWARD MOVEMENT OF SAID MOABLE GRID THEREBY TO PRODUCE A SHEARING ACTION BETWEEN THE BARS OF THE TWO GRIDS, THE LOWER ENDS OF THE BARS OF SAID MOVABLE GRID BEING FREE TO VIBRATE, AND MEANS POSITIONED TO BE ENGAGED BY SAID MOVABLE GRID AT THE END OF THE DOWNWARD DROP OF SAID MOVABLE GRID TO IMPART VIBRATION TO SAID LOWER ENDS OF THE BARS OF SAID MOVABLE GRID. 